A variable capacitance element using a MEMS (hereinafter, “MEMS capacitor”) has a fixed electrode, a movable electrode provided above the fixed electrode and an insulating film provided between the fixed electrode and the movable electrode. The movable electrode is formed on a sacrificial film formed by being coated on the fixed electrode.
In some cases, with the MEMS capacitor adopting this structure, the movable electrode is not formed flat due to concavities and convexities of an underlayer of the sacrificial film, that is, due to the fixed electrode positioned below the sacrificial film. For example, in an area which includes the end of the fixed electrode, coating characteristics of the sacrificial film curves a corresponding movable electrode downward. Hence, when the movable electrode is driven by being applied the voltage, the curved portion of the movable electrode contacts the end of the fixed electrode, and therefore planar portions of the fixed electrode and the movable electrode which occupy a large portion of the capacitor area do not sufficiently attach closely.
As a result, there is a problem that a MEMS capacitor included the movable electrode and the fixed electrode (and the insulating film formed on the fixed electrode) cannot provide a sufficient capacitance. Further, a switch element using the MEMS has a problem that a switching operation becomes unstable. As described above, a device formed using a conventional MEMS has a problem that good element characteristics cannot be obtained.